Chapter 20, Problem 20.38P

(a)

Interpretation Introduction

Interpretation:

The synthesis of diene has to be shown from cyclopentanone and acetylene.

Concept introduction:

Dehydration reaction:

Removal of water molecule from the reaction when the alcohol is treated with strong acid like sulfuric acid.

Alcohol is reaction with concentrated sulfuric acid, first alcohol gets protonated forms carbocation (more stable carbocation) followed by elimination of proton (${\text{H}}^{\text{+}}$) yields alkene as a product. The stability of carbocation is given below,

Tertiary carbocation is more stable than the secondary, secondary carbocation is more stable than primary.

In dehydration reaction, sulfuric acid is act as a proton donor, and which is used to protonate the alcohol and makes carbocation therefore sulfuric acid is the driving force of the reaction. Dehydration reaction will not go without acid (sulfuric acid).

Hydrogenation:

Palladium on carbon (Pd/C) or Pd/ CaCO₃ is used as a catalyst for hydrogenation of alkenes and alkynes.

(b)

Interpretation Introduction

Interpretation:

Stereochemistry of the dicarboxylic acid has to be rationalized.

Concept introduction:

Chiral:

A molecule is non superimposable on its mirror image is called chiral molecule.

Four different atoms attached to a carbon atom is called chiral molecule.

Isomer: A molecule having the same molecular formula but with different chemical structure is called isomer.

Stereoisomers: Stereoisomers are molecules that have the same molecular formula and they differ only in arrangement of atom in three-dimensional space.

Enantiomers: A compound which is non-superimposable mirror image is called enantiomers.

Diastereomers: A compound which is non-superimposable and non-mirror image is called diastereomers.

Racemic mixture: A racemic mixture is simply a mixture containing an equal amount of each enantiomer.